You're trying to link C code from C++, and it doesn't work because of name mangling (google for it).In the header files inside the "Tinkerforge bindings 1.0.24" group in your Xcode project, add the following in the top of the file:

#ifdef __cplusplusextern "C" {#endif

And the following in the bottom of the file:

#ifdef __cplusplus}#endif

Do this for every header file in the "Tinkerforge bindings 1.0.24" group of the project.

_________________RealBasic beginnerI'm not a native english speaker, sorry for my grammar.